In the digital age, the question of what constitutes “identity” becomes ever more complex, and the threat of identity theft continues to alarm. There is a growing literature on the problems of identity management and issues such as trustworthiness and privacy. In the past, solutions based on central authorities have been explored, but the difficulty of reconciling them with a networked world which is completely decentralised by its very nature has led to only partial adoption of these solutions. A practical line of development is by federating heterogeneous identity management frameworks. But there are much deeper research questions that should be addressed: what is a digital identity for Internet users, companies and for other institutions; is a digital identity unique in the Internet or is it only meaningful within a certain scope, such as a geographical locality or a limited time window; how does identity interact with privacy and how is trust defined among identities.